As a system that performs communication between a server and radio equipment, there has been a system using, for example, virtual network computing (VNC). In this system, the server receives input information inputted by an operation unit of the radio equipment, and executes an application program in accordance with the input information, and further, generates screen data based on the execution result of the program and transmits the generated screen data to the radio equipment. The radio equipment displays, on a display unit, a screen based on the screen data received from the server to accept input by the operation unit on the displayed screen. In each of Patent Literatures 1 to 3 cited later, a system as mentioned above is described.
Taking an electronic mail as one example, while normal character input or the like can be performed on the screen by operating a key on the radio equipment side, it is the server that actually executes a mailer, and the radio equipment only transmits the inputted key information to the server. The server generates a screen image tailored to a size of the screen of the equipment based on the key information received from the radio equipment to transmit the screen image to the radio equipment. Accordingly, the screen displayed on the radio equipment is generated not by the radio equipment but by the server. The radio equipment thus needs to be at least provided with a screen display function, a key input function and a communication function, and does not need to load an application program and various types of data (screen data, font data and the like). This can reduce cost and ensure high security against theft and the like.
In Patent Literatures 4 and 5 cited later, transmission of data of an initial screen from a server to a terminal is described. In a system of Patent Literature 4, once the terminal makes a connection to the server, the server transmits, to the terminal, desktop image information, application instruction information, and image information of the initial screen corresponding to the server. In the terminal, when a desktop image is selected from a displayed list to select an application, the connection to the corresponding server is made, and the application functioning on the server becomes available. A system of Patent Literature 5 is an electronic conferencing system in which TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are switched to perform data communication. When a connection request from the terminal to the server is performed, and once sharing of a screen is permitted in the server, initial screen data is transmitted in UDP from the server to the terminal, so that the screen data is transmitted in UDP every time there is an update in a shared screen area.